Replace ? characters when copying files to devices (since they're invalid on FAT32 filesystems), and check the return value of QDir::mkpath. Fixes issue #721.

src/core/filesystemmusicstorage.cpp

@@ -32,8 +32,12 @@ bool FilesystemMusicStorage::CopyToStorage(const CopyJob& job) {
     return true;
 
   // Create directories as required
+  const QString dest_directory = dest_filename.section('/', 0, -2);
   QDir dir;
-  dir.mkpath(dest_filename.section('/', 0, -2));
+  if (!dir.mkpath(dest_directory)) {
+    qWarning() << "Failed to create directory" << dest_directory;
+    return false;
+  }
 
   // Remove the destination file if it exists and we want to overwrite
   if (job.overwrite_ && QFile::exists(dest_filename))

src/core/organiseformat.cpp

@@ -154,6 +154,7 @@ QString OrganiseFormat::TagValue(const QString &tag, const Song &song) const {
   // Replace characters that really shouldn't be in paths
   value.replace('/', '_');
   value.replace('\\', '_');
+  value.replace('?', '_');
 
   return value;
 }